Field structure for dynamo-electric machines.



A. B. FIELD.

FIELD STRUCTURE FOR DYNAMO ELECTRIC MACHINES.

APPLICATION I ILED JAN. 22, 1906.

IIIIIHH! IHIIH/IlH/IHH Patented Fame, 1909.

INVENTUR:

Allan B -H'eld 4 4 ATTURNEY MTNE'SSE'S" (To all whom it may concern: I

subject of the King of England, residing at UNIT D STATES PATENT OFFICE.

ALLAN B. FIELD, OF NORWOOD, OHIOQASfiG'NQR TO BULLOCK ELEC IRICFACTURING CQMZPAN'L'A OORYORATION OF OHIO.

new s'rnoo'ronn ron nmmmnmomc'wmns.

Be, it known that I ALLAN B. FIELD, a

Norwood, in the county of Hamilton and .State of Ohio, have inventedcertain new and useful Improvements in Field Structures forDynamo-Electric Machines, of which" the following is .a. full, clear,and exact specifioation. My invention relates to dynamo-electricandparticularly to the construction and arrangement of the field coilsor windings on the rotatable elements of high speed alternators.

In the ordinary construction of rotating field element for alternatingcurrent generaters, the coils are formed from strap copper edgewisewound, the individual layers at all parts of the ooilsbcing normal tothe coil When this construction is applied to rotating elements of n" mesuch as turbo-clternetors, teeoils or windings are subjected to suchenormous centnifiigal.

' forces that they may be strained or distorted.

em to In a rotating field element, centrifugal portion of a coil acts inthe radially may be divided into two components, one parallel to the axiof the pole an th her normal thereta. componen parallel to the axis ofth pole is, in the usual construction, directed against the pole tip) 0pole shoe, and the normal component is 1- anced only by the strength andstiflncss of the coil itself. Therefore the stresses between adjacenttur or layers consist of a normalpressure, end a shearing stress whichtends to displace the turns. It is easily seen that certain portions ofthe coils are under practically no stress whatever and other portions,viz. the sides of the coils or the portions between adjacent poles areunder considerable stress. It is also seen that the greater the width ofthe pole pieces, the greater will be the normal component and hence theshearing stress, Several methods have been proposed for avoiding thisdifliculty, as by bracing the sides of the coils on adjacent poles bymeans of wedges fastened to the core or poles. It has also been proposedto ploy coils of edgewise wound strap cop er,

1 t wedge-shaped or w th converging si es and to support these oo1ls onwedge sha polepieoes or 111 radial slots in a cylindrical core. In thelatter case the center lines of pieces and which a radius. This forceact ng Patented rat. 1;, 1909.

the sides -of the coils coincide with radiiof the rotating field elementand the centrifugal forces acting along these lines will be taken up bythe pole tips or shoes, or by the retaining wedges in the slots, andthere is no tendency for coils so constructed to become distorted. Theabove constructions are not suitable for all types of machines.

The object of my invention is to provide for high [speed dynamo-electricmachines coils which can be easily applied to the pole are soconstructed that there will be little or no danger of portions of thecoils being displaced or distorted.

In carrying out my invention 1 rovide the rotatable member with coils oedgewise wound strap copper or other mater al, t e portions of thelayers of coil which are sub ect to shearing stresses due t centrifugaltome and to bulge coils outmwd away from the polemolmedtothcpolecmsetananglesuohthat said shearing stresses are reducedto a In machines of ordinary construction the shearing st esses tendingto bulge the ootwar or tov cause the layers to be shifted away from thepole can be made negligible or reduced to a .mimmmn by bending the s desof the coils at on angle such that the side portions of the innermostlayers are at r angles to redo extend-mg frorn the use p therototcblo'meneber to said mnermost My invention may be further brieflysumma ried as consisting in the construction and c mbination of partshereinafter set forth in the following description, drawings and claims.a 1

For a better understimding of my invention, reference is had to theaccompanying drawings, in which- Figure 1 is an elevation of a.portionof a rotatable field'element of a dynamo-electric machine, partsbeing shown in section; and- Fi 2 is a sectional elevation of one of tho e pieces and a coil thereon, the pole being I 'the coil. tions of thelayers'may be arc-shaped.

arallcl opposite sides-which plole pieces may e fastened to the rim by te usual dovetailed construction orby any other desired means. '1 helamina; are preferably held together by rivets 13. Segmental side plates14 are attached to the sides of the run by screws or bolts 15.

Mounted on the pole pieces are field coils 16 of novel construction. Thecoils which are previously formed of edgewisewound strap co per or othergood conducting material, eac have parallel ends 17 and parallel sides18, the center lines of the ends and sides being all parallel to'eachother. 'lhc coils can thus be easily appliedto the )ole pieces. turns orlayers of a cell being normal to the axis of the pole and to the centerlines of the sides and'ends of the coil as in the usual construction,the sides of the individual layers of the coil or the portions of theindividual layers between the ole pieces are inclined to the axis of thepo e orcoil and to the center lines of the sides 18. Ihis isaccomplished preferably by bendin the ends 17 of the coils as at 19,adjacent t 1e sides 18,the layers at the ends 17 of 1 the coils beinstraight and parallel for the greater width 0 If desired however, theend por- The angle to which theiside ortions of the layers are inclinedwill depen somewhat on the design of the machine, especially thediameter of the core or spider. and the width of the layers. In allcases the angle will be such that the shearing stress at any portion ofa coil will be reduced to a minimum. In an ordinary alternator in whichthe diameter of 'the spider is considerable as compared with the lengthof the poles the shearing stresses between the layers can be made almostnegligible by bending the coils to such an extent that the sides oftheinnermost turns or layers are normal to radii drawn through theircenters. In this case the angles between the layers remote from theinnermost layer and construction is shown in the drawings.

radii drawn through their centers will be slightly greater than ninetydegrees, the angle becoming gradually greater from the innermost to theoutermostvla er. However in practice, if the innermost ayer is normal toa radius drawn through its center,,the (lifference in the angles made bythe radii and the different layers will be so slight that all the layerswill be substantially normal to radii drawn through their centers. 'gllilis coils rest on seats 20, the outer faces of which are so shaped asto rpperly support the coils and the latter are e in place by pole tips21, which are undercut as shown.

as in Fig. -1, but the parts are shown out'of In Fig. 2, the sameconstruction is shown their true proportion to illustrate more clearlymy invention. In this figure, 0 rep- Instead of all parts of the indivirual' resents the center of rotation, 0A the axis of the pole and cod, OBa radlus normal to the innermost layer and drawn through its center, andCD the center line of the side of the coil, which line is parallel tothe axis of the coil. In actual machines, however, which "ave a core orspider of very ,small diameter, if a radius drawn through thecenter-of-mass of the side of the coil, or in other words through thecenter of the quadrilateral which represents a section of the side ofthe coil, cuts the outer portions of the coil sectionxat a point beyondthe pole tip, it will be impossi-.

- le to eliminate entirely the shearing stresses by bending the coilsuntil the innermost layer is normal to a radius drawn through itscenter. In this case in order that the maximum shear may be made assmall as possible, the angle made b the innermost layer and a radiusmust be s ightly less than ninety dcgrces and this angle, which can beaccurately determined, will depend on the design of the i machine.

It will be seen that there will be little tendency for any ortion of thesides to become displaced for t re reason that each layer has a supportwhich receives directly, practically all the stresses of that layer dueto centrifugal force. For example the force acting on the innermostlayer is transmitted directly to the next adjacent layer, and from layerto layer to the ploletip. In the construction shown, since t e ang esbetweenthe radii and the outermost layers are slightly greater thanninety degrees, there will be a tendency for such a pieces instead ofoutward.

. I aim in my claims to cover all modifications which do not involve adeparture from the s irit and scope of my invention.

W at I claim as new and desire to secure by Letters Patent is electricmachine, a lurality of pro ecting pole pieces having fie d coils, thepro ortions of each pole surrounded by the coil eing of substantiallyuniform cross section at all points, said coils being formed of edgewisewound strapconducting material and portions of tlte coils being bent sothat ortions of the individual layers of each coil etween adjacent polesare inclined to the axis of the pole on WL1Cl1 the coil is mounted at anangle such that the shearing stresses due to centrif-- ,electricmachine, (pole pieces having parallel opposite sides, an

coils thereon composed of ioo yers to move inward toward the pole v 1.In a rotatable member of a dynamo superposed layers of edgewise" woundstrap conducting material, the sides of the innermost layers of eachcoil being substantially normal to radii extending from the axis'of therotatable member to said innermost layers,

' whereby the shearing stresses due to centrifugal force and tending toshift the layers outward away from the pole are reduced to a minimum.

3. In a dynamo electric machine, a rotatable member having a pluralityof projecting poles and a winding consisting of coils of edgewise woundconducting material, portions of la ers at the ends of each coil beingin parallel p anes normal to the axis of the pole and the ortions of thela ers at the sides of each coil being in aralle planes which areinclined to the axle of the pole at such an angle that the shearingstresses due to centrifugal force and tending to shift the layersoutward away from the pole are reduced to a minimum.

4. In a dynamo electric machine, a rotatable field member provided withprojecting Eole pieces having parallel opposite sides,

eld coils thereon, each formed of edgewise wound straY conductingmaterial, the ortions of the ayeis at the sides of each coi beinginclined to the axis of the pole at an angle such that the shearingstresses between the layers due to centrifugal force and tending toshift the layers outward away from the pole are reduced to a minimum,and pole tips having undercut ortions engaging the coils and retainingthe atter in place. In testimony whereof I afiix my signature, in thepresence of two witnesses.

ALLAN B. FIELD. Witnesses: I

An'rmm F. Kwrs, FRED. J KINSEY.

